Colorless optical remote antenna units for broadband wireless access networks

In the future broadband wireless access networks, many remote antenna units (RAUs) are required to connected to a center office. To differentiate each RAU, wavelength-division multiplexing (WDM) is an efficient and mostly-used way, but this would require expensive wavelength-specific or wavelength-tunable optical sources. To reduce the cost, colorless or wavelength-independent RAU is highly desirable. In this paper, two approaches to realize the colorless RAUs based on the gain saturation effect or cross-polarization modulation in semiconductor optical amplifiers (SOAs) are reported. Full-duplex radio-over-fiber (RoF) links based on the colorless RAUs are constructed and evaluated.